Drive Circuit and Impedance Matching Device

ABSTRACT

A drive circuit performs switching between an on-state and an off-state of a PIN diode, the drive circuit being provided with a switching element and a switching element, a drive power supply, and a current limiting resistor that adjusts a forward current of the PIN diode. When the switching element is in an on-state and the switching element is in an off-state, the PIN diode is switched to the on-state by applying a forward voltage to the PIN diode from the drive power supply via the current limiting resistor, and when the switching element is in the off-state and the switching element is in the on-state, the PIN diode is switched to the off-state by applying, not via the current limiting resistor, a reverse voltage to the PIN diode from the drive power supply.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP2017/041328 which has anInternational filing date of Nov. 16, 2017 and designated the UnitedStates of America.

FIELD

The present disclosure relates to a drive circuit for switching betweenan on-state and an off-state of a PIN diode, and an impedance matchingdevice using the drive circuit.

BACKGROUND

The diode has a characteristic that it becomes in a conductive state(on-state) when a forward voltage is applied and becomes in an openstate (off-state) when a reverse voltage is applied.

Using this characteristic, a diode may be used as a switch. As such adiode, for example, a PIN diode is used. Japanese Patent Laid-OpenPublication No. 2003-110407 discloses an example of a drive circuit thatswitches between an on-state and an off-state of a conventional PINdiode. The drive circuit disclosed in this document has two switchingelements, a bias power supply +VD is supplied to an output terminal ofthe drive circuit when the switching element disposed on a positive sideof a power supply is in the on-state, and the bias power supply −VS issupplied to the output terminal of the drive circuit when the switchingelement disposed on a negative electrode side of the power supply is inthe on-state. The output terminal is connected to an input terminal ofthe PIN diode, and when the bias power supply +VD is supplied to theinput terminal, a forward voltage is applied to the PIN diode to turn onthe PIN diode. On the other hand, when the bias power supply −VS issupplied to the input terminal, a reverse voltage is applied to the PINdiode, to turn off the PIN diode.

SUMMARY

In the Japanese Patent Laid-Open Publication No. 2003-110407, the PINdiode is connected to a power supply line connecting a high-frequencyinput unit and a high-frequency output unit, and switching between theon-state and the off-state of the PIN diode is performed in a statewhere high-frequency current flows. The switching in such a conductionstate is called a “hot switching.” Particularly, as described in theJapanese Patent Laid-Open Publication No. 2003-110407, in hot switchingin a state where a high-frequency current flows, switching time from theon-state to the off-state of the PIN diode is long (switching speed isslow), that is, when a transition time of carriers of the PIN diode islong, power loss becomes large. Due to this power loss, for example,there was a problem in which an amount of heat generated by the PINdiode increases, thus reducing a reliability of the PIN diode.Therefore, when switching the PIN diode from the on-state to theoff-state, it was necessary to perform the switching with a shortertransition time.

In order to solve such a problem, a drive circuit disclosed in JapanesePatent No. 5050062 includes a bootstrap circuit, a clamp network, andthe like, and adjusts the switching speed. However, since the bootstrapcircuit, the clamp network and the like are used, circuit configurationand control are complicated.

Therefore, the present disclosure has been made in view of theaforementioned problems, and it is therefore an object of the presentdisclosure to provide a drive circuit capable of suppressing a reductionin reliability of a PIN diode due to hot switching with a simple circuitconfiguration, and to provide an impedance matching device using thedrive circuit.

A drive circuit provided by an aspect of the present disclosure is adrive circuit for switching between an on-state and an off-state of aPIN diode, the drive circuit comprising: a first switching element and asecond switching element, one of the first switching element and thesecond switching element being in an off-state when the other is in anon-state; a drive power supply that generates a DC voltage; and acurrent-limiting resistor that adjusts a forward current of the PINdiode, wherein when the first switching element is in the on-state andthe second switching element is in the off-state, a forward voltage isapplied from the drive power supply to the PIN diode via thecurrent-limiting resistor to turn on the PIN diode, and wherein when thefirst switching element is in the off-state and the second switchingelement is in the on-state, a reverse voltage is applied not via thecurrent-limiting resistor to the PIN diode from the drive power supplyto turn off the PIN diode. According to this configuration, whenswitching the PIN diode from the on-state to the off-state, since areverse voltage is applied to the PIN diode not via a current-limitingresistor, the PIN diode may be switched to the off-state in a shorttransition time. As a result, the amount of heat generated by the PINdiode can be suppressed. Therefore, deterioration of the reliability ofthe PIN diode due to hot switching can be suppressed.

In a preferred embodiment of the drive circuit, an on-resistance of thesecond switching element is 0.1Ω or less. According to thisconfiguration, since a resistance value in a current path when the PINdiode is changed from the on-state to the off-state is low, thetransition time from the on-state to the off-state of the PIN diode canbe further shortened.

In a preferred embodiment of the drive circuit, the forward current ofthe PIN diode generated by the forward voltage is determined by anon-resistance of the first switching element and the current-limitingresistor, and wherein a resistance value of the current-limitingresistor is determined based on the on-resistance of the first switchingelement so that the forward current of the PIN diode has a predeterminedcurrent value. According to this configuration, the forward current isset to be a predetermined current value (for example, 1 A or more),whereby the PIN diode may be switched from the off-state to the on-statewith a transition time sufficiently shorter than a carrier lifetime ofthe PIN diode.

In a preferred embodiment of the drive circuit, the first switchingelement, the current-limiting resistor, and the second switching elementare connected in series in this order from a positive electrode terminalto a negative electrode terminal of the drive power supply, and whereinan anode terminal of the PIN diode is connected to a node between thecurrent-limiting resistor and the second switching element and a cathodeterminal of the PIN diode is grounded. According to this configuration,when the first switching element is in the on-state and the secondswitching element is in the off-state, the forward voltage is applied tothe PIN diode via the current-limiting resistor, while when the firstswitching element is in the off-state and the second switching elementis in the on-state, the reverse voltage can be applied to the PIN diodenot via the current-limiting resistor. Therefore, in the current pathwhen the PIN diode is changed from the on-state to the off-state, it ispossible not to pass the current-limiting resistor.

In a preferred embodiment of the drive circuit, the current-limitingresistor, the first switching element, and the second switching elementare connected in series in this order from a positive electrode terminalto a negative electrode terminal of the drive power supply, and whereinan anode terminal of the PIN diode is connected to a node between thefirst switching element and the second switching element and a cathodeterminal of the PIN diode is grounded. With this configuration as well,in the current path when the PIN diode is changed from the on-state tothe off-state, it is possible not to pass the current-limiting resistor.

In a preferred embodiment of the drive circuit, the second switchingelement, the current-limiting resistor, and the first switching elementare connected in series in this order from a positive electrode terminalto a negative electrode terminal of the drive power supply, and whereinan anode terminal of the PIN diode is grounded and a cathode terminal ofthe PIN diode is connected to a node between the current-limitingresistor and the second switching element. With this configuration aswell, in the current path when the PIN diode is changed from theon-state to the off state, it is possible not to pass thecurrent-limiting resistor.

In a preferred embodiment of the drive circuit, the second switchingelement, the first switching element, and the current-limiting resistorare connected in series in this order from a positive electrode terminalto a negative electrode terminal of the drive power supply, and whereinan anode terminal of the PIN diode is grounded and a cathode terminal ofthe PIN diode is connected to a node between the first switching elementand the second switching element. With this configuration as well, inthe current path when the PIN diode is changed from the on-state to theoff-state, it is possible not to pass the current-limiting resistor.

In a preferred embodiment of the drive circuit, a filter circuit isfurther provided between the node and the PIN diode. According to thisconfiguration, since a high-frequency power is suppressed from beinginput to the first switching element and the second switching element bythe filter circuit, it is possible to suppress the elements from beingdamaged.

In a preferred embodiment of the drive circuit, the drive circuitfurther comprises a speed-up capacitor connected in parallel to thecurrent-limiting resistor. According to this configuration, when thefirst switching element is switched to the on-state and the secondswitching element is switched to the off-state, the current path throughthe speed-up capacitor is conducted. Therefore, since the PIN diode canbe switched to the on-state by a large current, the PIN diode can beswitched to the on-state with a short transition time.

An impedance matching device provided by a second aspect of the presentdisclosure is a impedance matching device arranged between ahigh-frequency power supply and a load connected to each other by apower supply line, the device comprising: a plurality of impedanceadjustment capacitors connected in parallel and each having one endconnected to the power supply line; a plurality of PIN diodes connectedin series one by one to corresponding ones of the plurality of impedanceadjustment capacitors; a plurality of drive circuits according to anyone of claims 1 to 9 respectively connected to corresponding ones of theplurality of PIN diodes; a detection unit that detects a load-sideimpedance seen from an output end of the high-frequency power supply;and a control circuit that inputs a drive signal for switching betweenan on-state and an off-state of the first switching element and thesecond switching element to each of the plurality of drive circuitsbased on the load-side impedance. According to this configuration, sincethe impedance adjustment capacitor connected to the PIN diode which isin the on-state becomes effective by switching between the on-state andthe off-state of the PIN diode, it is possible to change the capacitanceof the impedance matching device. As a result, it is possible to adjustload-side impedance and perform impedance matching. In addition, sincethe transition time of switching of the PIN diode from the on-state tothe off-state is short, speed of the impedance matching is improved.Therefore, it is possible to efficiently supply the high-frequency powerfrom the high-frequency power supply to the load.

Effect of Invention

According to the present disclosure, when the PIN diode is switched fromthe on-state to the off-state, a reverse voltage is applied not via thecurrent-limiting resistor to the PIN diode. Thus, with a simpleconfiguration, the PIN diode can be switched from the on-state to theoff-state with a short transition time. Therefore, deterioration of thereliability of the PIN diode due to hot switching can be suppressed.

The above and further objects and features will more fully be apparentfrom the following detailed description with accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit configuration diagram illustrating a drive circuitaccording to a first embodiment.

FIG. 2 is a circuit configuration diagram illustrating a drive circuitaccording to a second embodiment.

FIG. 3 is a circuit configuration diagram illustrating a drive circuitaccording to a third embodiment.

FIG. 4 is a circuit configuration diagram illustrating a drive circuitaccording to a fourth embodiment.

FIG. 5 is a diagram illustrating the overall configuration of ahigh-frequency power supply system according to a fifth embodiment.

FIG. 6 is a diagram illustrating the configuration of an impedancematching device according to a fifth embodiment.

DETAILED DESCRIPTION

Preferred embodiments of the present disclosure will be described belowwith reference to the drawings.

FIG. 1 illustrates a circuit configuration of a drive circuit A1 of aPIN diode D according to a first embodiment. The drive circuit A1receives an input from a drive power supply (not illustrated) andapplies a forward bias or a reverse bias to the PIN diode D via anoutput terminal OUT. An anode terminal of the PIN diode D is connectedto the output terminal OUT of the drive circuit A1 and connected to apower supply line L through which a high-frequency current flows. Acathode terminal of the PIN diode D is grounded. Further, the drivepower supply is a DC voltage supply and has a positive electrodeterminal V+ and a negative electrode terminal V−. The positive electrodeterminal V+ applies a forward voltage drop (a voltage required to allowa forward current to flow) to an anode terminal of the PIN diode D whena switching element SH to be described later is in the on-state and aswitching element SL to be described later is in the off-state to turnon the PIN diode D. Further, an negative electrode terminal V− is forapplying a negative voltage (a voltage in a range not reaching abreakdown voltage) to the anode terminal of the PIN diode D to turn offthe PIN diode D when the switching element SL is in the on-state and theswitching element SH is in the off-state.

The drive circuit A1 applies a forward voltage to the PIN diode D viathe output terminal OUT to bring the PIN diode D into a conductancestate (on-state), and applies a reverse voltage to the PIN diode D tobring the PIN diode D in an open state (off-state).

As illustrated in FIG. 1, the drive circuit A1 includes two switchingelements SH and SL, a current-limiting resistor R, a speed-up capacitorSC, and a filter circuit F.

The switching elements SH and SL are circuit elements made ofsemiconductors and are, for example, metal oxide semiconductor fieldeffect transistor (MOSFET), bipolar transistor, insulated gate bipolartransistor (IGBT), optocoupler and the like. In the present embodiment,an example in which an N-channel MOSFET is used as the switchingelements SH and SL will be described as an example, but the presentdisclosure is not limited thereto.

In the switching elements SH and SL, a drive signal is input from acontrol circuit (not illustrated) to the gate terminal, and the on-stateand the off-state are switched in accordance with the drive signal. Theswitching elements SH and SL are controlled such that when one of themis in the on-state, the other is in the off-state by the drive signal.For example, the control circuit generates two voltage signals whosehigh levels and the low levels are mutually inverted, inputs one of thevoltage signals as a drive signal S1 to the switching element SH, andinputs the other of the voltage signals as a drive signal /S1 to aswitching element SL. In a case where the drive signal S1 (/S1) is ahigh-level voltage signal, the switching element SH (SL) is turned on,and in a case where the drive signal S1 (/S1) is a low-level voltagesignal, the switching element SH (SL) is turned off. As a result, theon-states and the off-states of the switching element SH and theswitching element SL are opposite to each other. In the presentembodiment, the switching element SH corresponds to a “first switchingelement” recited in the claims, and the switching element SL correspondsto a “second switching element” recited in the claims.

In the drive circuit A1, the switching elements SH and SL are connectedin series via a current-limiting resistor R. The switching element SH isconnected to the positive electrode side of the drive power supply andthe switching element SL is connected to the negative electrode side ofthe drive power supply. Therefore, in the drive circuit A1, theswitching element SH (first switching element), the current-limitingresistor R, and the switching element SL (second switching element)connected in series in this order from the positive electrode terminalV+ to the negative electrode terminal V− of the drive power supply.Specifically, a drain terminal of the switching element SH is connectedto the positive electrode terminal V+ of the drive power supply, and asource terminal of the switching element SH is connected to one end ofthe current-limiting resistor R. Further, a drain terminal of theswitching element SL is connected to the other end of thecurrent-limiting resistor R, and a source terminal of the switchingelement SL is connected to the negative electrode terminal V− of thedrive power supply. The gate terminals of the switching elements SH andSL are connected to the control circuit.

In addition, a speed-up capacitor SC is connected in parallel to thecurrent-limiting resistor R. A node a between the current-limitingresistor R and the switching element SL is connected to the outputterminal OUT via a filter circuit F. The filter circuit F is constitutedby, for example, a capacitor Fc and an inductor Fl connected in an Lshape. Specifically, one end of the inductor Fl and one end of thecapacitor Fc are connected to the node a. The other end of the inductorFl is connected to the output terminal OUT, and the other end of thecapacitor Fc is grounded. The configuration of the filter circuit F isnot limited thereto. It is not necessary to include the filter circuitF, but, in a case where the filter circuit F is included, ahigh-frequency power flowing through an RF input terminal and an RFoutput terminal may be suppressed from being input to the drive circuitA1, thus suppressing damages to the switching elements SH and SL.

The operation when the drive circuit A1 configured as described aboveswitches between the on-state and the off-state of the PIN diode D willbe described.

First, the operation when the PIN diode D is switched from the off-stateto the on-state will be described.

When the switching element SH is switched to the on-state and theswitching element SL is switched to the off-state when the PIN diode Dis in the off-state, that is, the switching element SH is in theoff-state and the switching element SL is in the on-state, a currentpath is conducted from the positive electrode terminal V+ of the drivepower supply to the anode terminal of the PIN diode D via the switchingelement SH, the current-limiting resistor R or the speed-up capacitorSC, and the filter circuit F. As a result, a forward voltage is appliedto the PIN diode D, and the PIN diode D is turned on. At this time, atthe moment when the switching element SH is switched from the off-stateto the on-state and the switching element SL is switched from theon-state to the off-state, a large forward current flows through the PINdiode D via the current path passing through the speed-up capacitor SC.Further, when charging of the speed-up capacitor SC is completed, aforward current flows via the current path passing through thecurrent-limiting resistor R to the PIN diode D. The forward current isdetermined by the current-limiting resistor R and the on-resistance ofthe switching element SH. Here, it is possible to supply a sufficientforward current to the PIN diode D by setting the current-limitingresistor R so that the forward current becomes a predetermined currentvalue (for example, 1 A or more). Thus, when the PIN diode D is switchedfrom the off-state to the on-state, the switching can be performed witha transition time that is sufficiently shorter than a carrier lifetimeof the PIN diode D.

Next, the operation when the PIN diode D is switched from the on-stateto the off-state will be described.

When the switching element SH is switched to the off-state and theswitching element SL is switched to the on-state when the PIN diode D isin the on-state, that is, the switching element SH is in the on-stateand the switching element SL is in the off-state, a current path isconducted from the negative electrode terminal V− of the drive powersupply to the anode terminal of the PIN diode D via the switchingelement SL and the filter circuit F. As a result, a reverse voltage isapplied to the PIN diode D, and the PIN diode D is turned off. At thistime, when the switching element SH is switched from the on-state to theoff-state and the switching element SL is switched from the off-state tothe on-state, current flows through the switching element SL not via thecurrent-limiting resistor R or the speed-up capacitor SC. Therefore,since the transition time when the PIN diode D is switched from theon-state to the off-state is determined by an on-resistance of theswitching element SL, the transition time may be made shorter than thatin a case where the current-limiting resistor R is present. For example,when the switching element SL having a small on-resistance (for example,0.1Ω or less) is used, the transition time may be shortened.

As described above, according to the drive circuit A1 according to thefirst embodiment, the PIN diode D may be switched from the on-state tothe off-state with a short circuit time with a simple circuitconfiguration. Therefore, it is possible to suppress a loss such as heatgeneration of the PIN diode D and to suppress deterioration of areliability of the PIN diode D by hot switching.

FIG. 2 illustrates a drive circuit A2 of the PIN diode D according to asecond embodiment. The same or similar components as those of the drivecircuit A1 are denoted by the same reference numerals, and descriptionthereof is omitted. As illustrated in the figure, the drive circuit A2of the second embodiment is different from the drive circuit A1according to the first embodiment in a connection position of thecurrent-limiting resistor R.

In the drive circuit A2, the current-limiting resistor R is connectedbetween the switching element SH and the positive electrode terminal V+of the drive power supply, and the switching element SH and theswitching element SL are directly connected to each other. Therefore, inthe drive circuit A2, the current-limiting resistor R, the switchingelement SH, and the switching element SL are connected in series in thisorder from the positive electrode terminal V+ to the negative electrodeterminal V− of the drive power supply. Specifically, the positiveelectrode terminal V+ of the drive power supply and one end of thecurrent-limiting resistor R are connected, and the other end of thecurrent-limiting resistor R and a drain terminal of the switchingelement SH are connected. Further, a source terminal of the switchingelement SH and a drain terminal of the switching element SL areconnected, and a source terminal of the switching element SL and thenegative electrode terminal V− of the drive power supply are connected.A node b between the switching element SH and the switching element SLis connected to the output terminal OUT via a filter circuit F. Further,in this embodiment, the switching element SH corresponds to the “firstswitching element” recited in the claims and the switching element SLcorresponds to the “second switching element” recited in the claims.

Since the drive circuit A2 configured as described above operates in thesame manner as the drive circuit A1 according to the first embodiment,the same effect may be obtained.

FIG. 3 illustrates a drive circuit A3 of a PIN diode D according to athird embodiment. The same reference numerals are given to the same orsimilar configurations as those of the drive circuits A1 and A2, and thedescription thereof will be omitted. The third embodiment differs fromthe first embodiment and the second embodiment in that connectiondirections of an anode terminal and a cathode terminal of the PIN diodeD are opposite. Specifically, the anode terminal of the PIN diode D isgrounded, and the cathode terminal of the PIN diode D is connected to apower supply line L connecting an RF input terminal and an RF outputterminal. Further, an output terminal OUT of a drive circuit A3 isconnected to the cathode terminal of the PIN diode D.

Further, the drive circuit A3 has a circuit configuration different fromthat of the drive circuit A1. More specifically, in the drive circuitA1, a node a between a switching element SL and a current-limitingresistor R is connected to the output terminal OUT via a filter circuitF, but in the drive circuit A3, a node c between a switching element SHand the current-limiting resistor R is connected to the output terminalOUT via the filter circuit F. In the present embodiment, the switchingelement SH corresponds to the “second switching element” recited in theclaims and the switching element SL corresponds to the “first switchingelement” recited in the claims Therefore, in the drive circuit A3, theswitching element SH (second switching element), the current-limitingresistor R, and the switching element SL (first switching element) areconnected in series in this order from the positive electrode terminalV+ to the negative electrode terminal V− of the drive power supply.

The operation in which the PIN diode D is switched between the on-stateand the off-state by the drive circuit A3 configured as described abovewill be described.

First, the operation in which the PIN diode D is switched from theoff-state to the on-state will be described.

When the switching element SH is switched to the off-state and theswitching element SL is switched to the on-state when the PIN diode D isin the off-state, that is, the switching element SH is in the on-stateand the switching element SL is in the off-state, a current path fromthe negative electrode terminal V− of the drive power supply to thecathode terminal of the PIN diode D is conducted via the switchingelement SL, the current-limiting resistor R or the speed-up capacitorSC, and the filter circuit F. As a result, a forward voltage is appliedto the PIN diode D, and the PIN diode D is turned on. At this time, atthe moment when the switching element SH is switched from the on-stateto the off-state and the switching element SL is switched from theoff-state to the on-state, a large forward current flows through thecurrent path via the speed-up capacitor SC to the PIN diode D. Further,when charging of the speed-up capacitor SC is completed, a forwardcurrent flows through the current path passing through thecurrent-limiting resistor R to the PIN diode D. The forward current isdetermined by the current-limiting resistor R and the on-resistance ofthe switching element SL. Here, as in the first embodiment, thecurrent-limiting resistor R is set so that the forward current becomes apredetermined current value (for example, 1 A or more), whereby asufficient forward current can be supplied to the PIN diode D. Thus,when switching the PIN diode D from the off-state to the on-state,switching can be performed with the transition time that is sufficientlyshorter than the carrier lifetime of the PIN diode D.

Next, the operation when the PIN diode D switches from the on-state tothe off-state will be described.

When the switching element SH is switched to the on-state and theswitching element SL is switched to the off-state when the PIN diode Dis in the on-state, that is, the switching element SH is in theoff-state and the switching element SL is in the on-state, a currentpath is conducted from the positive electrode terminal V+ of the drivepower supply to the cathode terminal of the PIN diode D through theswitching element SH and the filter circuit F. As a result, a reversevoltage is applied to the PIN diode D, and the PIN diode D is turnedoff. At this time, when the switching element SH is switched from theoff-state to the on-state and the switching element SL is switched fromthe on-state to the off-state, the current flows through the switchingelement SH not via the current-limiting resistor R or the speed-upcapacitor SC. Therefore, the transition time when the PIN diode D isswitched from the on-state to the off-state is determined by theon-resistance of the switching element SH, so the transition time can bemade shorter than that in a case where the current-limiting resistor Rexists. For example, if the switching element SH having a smallon-resistance (for example, 0.1Ω or less) is used, the transition timemay be shortened.

As described above, according to the drive circuit A3 in the thirdembodiment, the PIN diode D may be switched from the on-state to theoff-state with a short transition time using a simple circuitconfiguration. Therefore, it is possible to suppress a loss such as heatgeneration of the PIN diode D and to suppress deterioration ofreliability of the PIN diode D by hot switching.

FIG. 4 illustrates a drive circuit A4 of a PIN diode D according to afourth embodiment. The same reference numerals are given to the same orsimilar configurations as those of the drive circuits A1 to A3, and thedescription thereof will be omitted. As illustrated in the figure, thedrive circuit A4 of the fourth embodiment is different from the drivecircuit A3 of the third embodiment in the connection position of thecurrent-limiting resistor R.

In the drive circuit A4, the current-limiting resistor R is connectedbetween the switching element SL and the negative electrode terminal V−of the drive power supply, and the switching element SH and theswitching element SL are directly connected. Therefore, in the drivecircuit A4, the switching element SH (second switching element), theswitching element SL (first switching element), and a current-limitingresistor R are connected in series in this order from the positiveelectrode terminal V+ to the output terminal V− on the negative side ofthe drive power supply. Specifically, the positive electrode terminal V+of the drive power supply and a drain terminal of the switching elementSH are connected to each other, and a source terminal of the switchingelement SH and a drain terminal of the switching element SL areconnected to each other. Further, a source terminal of the switchingelement SL is connected to one end of the current-limiting resistor R,and the other end of the current-limiting resistor R is connected to thenegative electrode terminal V− of the drive power supply. A node dbetween the source terminal of the switching element SH and the drainterminal of the switching element SL is connected to an output terminalOUT via a filter circuit F. Further, in the present embodiment, theswitching element SH corresponds to the “second switching element”recited in the claims, and the switching element SL corresponds to the“first switching element” recited in the claims.

The drive circuit A4 configured as described above operates in the samemanner as the drive circuit A3 according to the third embodiment, sothat the same effect can be obtained.

The drive circuits A1 to A4 of the PIN diode D described above are used,for example, in an impedance matching device in a high-frequency powersupply system. The high-frequency power supply system will be describedbelow as a fifth embodiment of the present disclosure.

FIG. 5 illustrates an example of an overall configuration of ahigh-frequency power supply system according to a fifth embodiment ofthe present disclosure. In the same figure, the high-frequency powersupply system includes a high-frequency power supply 1, a load 2, and animpedance matching device 3. The high-frequency power supply 1 and theload 2 are connected by a power supply line 4, and an impedance matchingdevice 3 is disposed between them. The high-frequency power supplysystem is a system that supplies high-frequency power generated by thehigh-frequency power supply 1 to the load 2 via the power supply line 4.The power supply line 4 corresponds to a power supply line L in FIGS. 1to 4.

The high-frequency power supply 1 outputs the high-frequency power. Thehigh-frequency power supply 1 converts an AC power from a power systeminto a DC power by a rectifier circuit, converts the DC power into thehigh-frequency power by an inverter circuit, and outputs it. Inaddition, the high-frequency power supply 1 includes a power supplycontrol circuit (not illustrated), and controls the output power and theoutput current. In the present embodiment, the high-frequency powersupply 1 outputs, for example, a high-frequency power of 13.56 MHz. Aconfiguration and a frequency of the high-frequency power supply 1 arenot limited.

The load 2 performs various processes using the high-frequency powerinput from the high-frequency power supply 1. An example of such a load2 is a plasma processing apparatus, a plasma generation apparatus, or acontactless power transmission apparatus, or the like. For example, theplasma processing apparatus is a device that includes a workpieceprocessing unit and performs a process (for example, etching, CVD, etc.)on the workpiece such as a semiconductor wafer or a liquid crystalsubstrate carried into the work processing unit. In order to process theworkpiece, the plasma processing apparatus introduces a plasma dischargegas into the workpiece processing unit and applies the high-frequencypower (voltage) supplied from the high-frequency power supply 1 to theplasma discharge gas, thereby ionizing the plasma discharge gas to bebrought into a plasma state from a non-plasma state. The plasmaprocessing apparatus processes the workpiece by utilizing a gas in theplasma state. The plasma generation apparatus ionizes the plasmadischarge gas to be brought into a plasma state from a non-plasma state,and supplies the gas in the plasma state to a plasma chamber or thelike.

In the plasma processing apparatus, as a manufacturing process such asplasma etching and plasma CVD proceeds, the state of the plasma changesmomentarily. As a result, an impedance of the load 2 varies. Therefore,in order to efficiently supply electric power from the high-frequencypower supply 1 to the load 2, the high-frequency power supply systemincludes an impedance matching device 3 that adjust an impedance on theload 2 side seen from an output end of the high-frequency power supply 1(hereinafter, referred to as a “load-side impedance”) as the impedanceof the load 2 varies.

The impedance matching device 3 performs an impedance matching byadjusting the load-side impedance. The impedance matching device 3includes the drive circuit A1 and the PIN diode D according to the firstembodiment.

FIG. 6 illustrates an example of a detailed circuit configuration of theimpedance matching device 3. In the same figure, the impedance matchingdevice 3 includes an impedance detection unit 31, a control circuit 32,and an impedance adjustment circuit 33.

The impedance detection unit 31 is disposed at an input terminal of theimpedance matching device 3 and detects the load-side impedance. Theimpedance detection unit 31 outputs the load-side impedance thusdetected to a control circuit 32. Specifically, the impedance detectionunit 31 detects a current corresponding to the high-frequency currentflowing through the power supply line 4 and a voltage corresponding tothe high-frequency voltage generated in the power supply line 4, andobtains a current effective value, a voltage effective value, and aphase difference between the current signal and the voltage signal fromthe current signal and the voltage signal thus detected. Then, theload-side impedance is calculated using these parameters, and theload-side impedance thus calculated is outputted to the control circuit32. A configuration of the impedance detection unit 31 and a method ofdetecting the load-side impedance are not limited thereto.

The control circuit 32 controls the impedance adjustment circuit 33 sothat the load-side impedance inputted from the impedance detection unit31 becomes a predetermined impedance value (for example, the impedancewhen looking at the high-frequency power supply 1 from the output end ofthe high-frequency power supply 1).

The impedance adjustment circuit 33 includes a capacitance variationcircuit 331, a fixed capacitor 332, and an inductor 333. The fixedcapacitor 332 may not be included. The impedance adjustment circuit 33changes capacitance of the capacitance variation circuit 331 and adjuststhe load-side impedance.

The capacitance variation circuit 331 is configured to include aplurality of adjustment capacitors (impedance adjustment capacitors) Cd,a plurality of PIN diodes D, and a plurality of drive circuits A1,whereby the capacitance can be changed. In the capacitance variationcircuit 331, one PIN diode D is connected in series to each adjustmentcapacitor Cd, and series bodies of the adjustment capacitor Cd and thePIN diode D connected in parallel to each other. One end of eachadjustment capacitor Cd is connected to the power supply line 4, and theother end is connected to an anode terminal of each PIN diode D. Inaddition, a cathode terminal of each PIN diode D is grounded. Thecapacitances of the respective adjustment capacitors Cd are differentfrom each other, and are set so as to increase, for example, in a binarystep such as 1 pF, 2 pF, 4 pF, . . . . Capacitors having the samecapacitance may be used.

Further, the capacitance of each adjustment capacitor Cd is not limitedto the configuration in which all capacitances are different from eachother or all the capacitances are the same. A plurality of adjustmentcapacitors Cd whose capacitance increases, for example, in a binary stepsuch as 1 pF, 2 pF, 4 pF, . . . and one or a plurality of adjustmentcapacitors Cd having other capacitances (for example, 10 pF, etc.) maybe combined. In addition, it does not mean that a predeterminedcapacitance is realized with one capacitor. For example, in order toachieve a capacitance of 10 pF, capacitances of 5 pF may be connected inparallel or capacitances of 20 pF may be connected in series.

In addition, the capacitance variation circuit 331 may include acapacitance-invariant capacitor having one end connected to the powersupply line 4 and the other end grounded. The drive circuit A1 isconnected to each PIN diode D.

In the present embodiment, the fixed capacitor 332 and the inductor 333are connected in series to the power supply line 4, and the capacitancevariation circuit 331 is arranged on the upstream side of the powersupply line 4 from them in the impedance adjustment circuit 33, asillustrated in FIG. 6. The connection position between the fixedcapacitor 332 and the inductor 333 is not limited to the aforementionedconnection. For example, the capacitance variation circuit 331, thefixed capacitor 332, and the inductor 333 have only to be connected inan L-type connection, a π-type connection, a T-type connection and thelike.

In the impedance matching device 3 configured as described above, theload-side impedance detected by the impedance detection unit 31 isoutput to the control circuit 32. Then, the control circuit 32 generatesdrive signals S1 and /S1 to be input to each drive circuit A1 so thatthe load-side impedance input to the control circuit 32 becomes apredetermined impedance. The drive signals S1 and /S1 thus generated arerespectively input to the switching elements SH and SL of the respectivedrive circuits A1. As a result, the on-state and the off-state of thePIN diode D to which the drive circuit A1 is connected are switched bythe operation described in the first embodiment. Then, a high-frequencycurrent flowing through the power supply line 4 flows through theadjustment capacitor Cd connected to the PIN diode D which becomes inthe on-state, the adjustment capacitor Cd becomes effective, and acapacitance obtained by adding the capacitances of the adjustmentcapacitors Cd becomes the capacitance of the capacitance variationcircuit 331. In this manner, the impedance matching device 3 adjusts thecapacitance of the capacitance variation circuit 331 by controlling theon-state and the off-state of each PIN diode D, thereby adjusting theload-side impedance.

According to the high-frequency power supply system configured asdescribed above, the PIN diode D is switched between the on-state andthe off-state by the drive circuit A1. Thus, as illustrated in the firstembodiment, it is possible to suppress deterioration in the reliabilityof the PIN diode D due to hot switching, such that it is possible toappropriately switch between the on-state and the off-state of the PINdiode D. Therefore, impedance matching by the impedance matching device3 can be appropriately performed. In addition, since the drive circuitA1 can switch the PIN diode D from the on-state to the off-state with ashort transition time, the impedance matching device 3 can adjust theload-side impedance at high speed. Therefore, in the high-frequencypower supply system, it is possible to efficiently supply thehigh-frequency power from the high-frequency power supply 1 to the load2.

In the high-frequency power supply system according to the fifthembodiment, a case where the impedance matching device 3 detects theload-side impedance by the impedance detection unit 31, and the controlcircuit 32 controls the impedance adjustment circuit 33 based on theload-side impedance has been described as an example, but the inventionis not limited thereto. For example, instead of the impedance detectionunit 31, a reflected wave power detection unit for detecting reflectedwave power flowing through the power supply line 4 is provided, and thecontrol circuit 32 may control the impedance adjustment circuit 33 sothat the reflected wave power becomes low.

In the high-frequency power supply system according to the fifthembodiment, a case where the impedance matching device 3 includes thedrive circuit A1 according to the first embodiment has been described asan example, but instead of the drive circuit A1, the drive circuits A2to A4 according to the second to fourth embodiments may be included.Further, the drive circuits A1 to A4 may be combined.

The drive circuit of the PIN diode according to the present disclosureand the impedance matching device using the drive circuit are notlimited to the aforementioned embodiments. The specific configuration ofeach part of the drive circuit and the impedance matching device of thepresent disclosure can be variously changed in design.

It is to be noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise.

It is to be noted that the disclosed embodiment is illustrative and notrestrictive in all aspects. The scope of the present invention isdefined by the appended claims rather than by the description precedingthem, and all changes that fall within metes and bounds of the claims,or equivalence of such metes and bounds thereof are therefore intendedto be embraced by the claims.

1. A drive circuit for switching between an on-state and an off-state ofa PIN diode, the drive circuit comprising: a first switching element anda second switching element, one of the first switching element and thesecond switching element being in an off-state when the other is in anon-state; a drive power supply that generates a DC voltage; and acurrent-limiting resistor that adjusts a forward current of the PINdiode, wherein when the first switching element is in the on-state andthe second switching element is in the off-state, a forward voltage isapplied from the drive power supply to the PIN diode via thecurrent-limiting resistor to turn on the PIN diode, and wherein when thefirst switching element is in the off-state and the second switchingelement is in the on-state, a reverse voltage is applied not via thecurrent-limiting resistor to the PIN diode from the drive power supplyto turn off the PIN diode.
 2. The drive circuit according to claim 1,wherein an on-resistance of the second switching element is 0.1Ω orless.
 3. The drive circuit according to claim 1, wherein the forwardcurrent of the PIN diode generated by the forward voltage is determinedby an on-resistance of the first switching element and thecurrent-limiting resistor, and wherein a resistance value of thecurrent-limiting resistor is determined based on the on-resistance ofthe first switching element so that the forward current of the PIN diodehas a predetermined current value.
 4. The drive circuit according toclaim 1, wherein the first switching element, the current-limitingresistor, and the second switching element are connected in series inthis order from a positive electrode terminal to a negative electrodeterminal of the drive power supply, and wherein an anode terminal of thePIN diode is connected to a node between the current-limiting resistorand the second switching element and a cathode terminal of the PIN diodeis grounded.
 5. The drive circuit according to claim 1, wherein thecurrent-limiting resistor, the first switching element, and the secondswitching element are connected in series in this order from a positiveelectrode terminal to a negative electrode terminal of the drive powersupply, and wherein an anode terminal of the PIN diode is connected to anode between the first switching element and the second switchingelement and a cathode terminal of the PIN diode is grounded.
 6. Thedrive circuit according to claim 1, wherein the second switchingelement, the current-limiting resistor, and the first switching elementare connected in series in this order from a positive electrode terminalto a negative electrode terminal of the drive power supply, and whereinan anode terminal of the PIN diode is grounded and a cathode terminal ofthe PIN diode is connected to a node between the current-limitingresistor and the second switching element.
 7. The drive circuitaccording to claim 1, wherein the second switching element, the firstswitching element, and the current-limiting resistor are connected inseries in this order from a positive electrode terminal to a negativeelectrode terminal of the drive power supply, and wherein an anodeterminal of the PIN diode is grounded and a cathode terminal of the PINdiode is connected to a node between the first switching element and thesecond switching element.
 8. The drive circuit according to claim 4,further comprising a filter circuit connected between the node and thePIN diode.
 9. The drive circuit according to claim 1, further comprisinga speed-up capacitor connected in parallel to the current-limitingresistor.
 10. An impedance matching device arranged between ahigh-frequency power supply and a load connected to each other by apower supply line, the device comprising: a plurality of impedanceadjustment capacitors connected in parallel and each having one endconnected to the power supply line; a plurality of PIN diodes connectedin series one by one to corresponding ones of the plurality of impedanceadjustment capacitors; a plurality of drive circuits according to claim1 respectively connected to corresponding ones of the plurality of PINdiodes; a detection unit that detects a load-side impedance seen from anoutput end of the high-frequency power supply; and a control circuitthat inputs a drive signal for switching between an on-state and anoff-state of the first switching element and the second switchingelement to each of the plurality of drive circuits based on theload-side impedance.
 11. An impedance matching device arranged between ahigh-frequency power supply and a load connected to each other by apower supply line, the device comprising: a plurality of impedanceadjustment capacitors connected in parallel and each having one endconnected to the power supply line; a plurality of PIN diodes connectedin series one by one to corresponding ones of the plurality of impedanceadjustment capacitors; a plurality of drive circuits according to anyone of claim 3 respectively connected to corresponding ones of theplurality of PIN diodes; a detection unit that detects a load-sideimpedance seen from an output end of the high-frequency power supply;and a control circuit that inputs a drive signal for switching betweenan on-state and an off-state of the first switching element and thesecond switching element to each of the plurality of drive circuitsbased on the load-side impedance.
 12. An impedance matching devicearranged between a high-frequency power supply and a load connected toeach other by a power supply line, the device comprising: a plurality ofimpedance adjustment capacitors connected in parallel and each havingone end connected to the power supply line; a plurality of PIN diodesconnected in series one by one to corresponding ones of the plurality ofimpedance adjustment capacitors; a plurality of drive circuits accordingto claim 4 respectively connected to corresponding ones of the pluralityof PIN diodes; a detection unit that detects a load-side impedance seenfrom an output end of the high-frequency power supply; and a controlcircuit that inputs a drive signal for switching between an on-state andan off-state of the first switching element and the second switchingelement to each of the plurality of drive circuits based on theload-side impedance.
 13. An impedance matching device arranged between ahigh-frequency power supply and a load connected to each other by apower supply line, the device comprising: a plurality of impedanceadjustment capacitors connected in parallel and each having one endconnected to the power supply line; a plurality of PIN diodes connectedin series one by one to corresponding ones of the plurality of impedanceadjustment capacitors; a plurality of drive circuits according to claim5 respectively connected to corresponding ones of the plurality of PINdiodes; a detection unit that detects a load-side impedance seen from anoutput end of the high-frequency power supply; and a control circuitthat inputs a drive signal for switching between an on-state and anoff-state of the first switching element and the second switchingelement to each of the plurality of drive circuits based on theload-side impedance.
 14. An impedance matching device arranged between ahigh-frequency power supply and a load connected to each other by apower supply line, the device comprising: a plurality of impedanceadjustment capacitors connected in parallel and each having one endconnected to the power supply line; a plurality of PIN diodes connectedin series one by one to corresponding ones of the plurality of impedanceadjustment capacitors; a plurality of drive circuits according to claim6 respectively connected to corresponding ones of the plurality of PINdiodes; a detection unit that detects a load-side impedance seen from anoutput end of the high-frequency power supply; and a control circuitthat inputs a drive signal for switching between an on-state and anoff-state of the first switching element and the second switchingelement to each of the plurality of drive circuits based on theload-side impedance.
 15. An impedance matching device arranged between ahigh-frequency power supply and a load connected to each other by apower supply line, the device comprising: a plurality of impedanceadjustment capacitors connected in parallel and each having one endconnected to the power supply line; a plurality of PIN diodes connectedin series one by one to corresponding ones of the plurality of impedanceadjustment capacitors; a plurality of drive circuits according to claim7 respectively connected to corresponding ones of the plurality of PINdiodes; a detection unit that detects a load-side impedance seen from anoutput end of the high-frequency power supply; and a control circuitthat inputs a drive signal for switching between an on-state and anoff-state of the first switching element and the second switchingelement to each of the plurality of drive circuits based on theload-side impedance.